Bar Magnet

Bar Magnet is a magnet that is rectangular in shape and has two poles, the North Pole and South Pole. The magnetic field of a bar magnet is maximum at its pole and minimum at its center. Bar Magnets are made up of Iron, cobalt, or any other Ferromagnetic materials that show magnetic properties. Bar magnets can be of various types including Cylindrical Bar magnets and Rectangular Bar magnets.

Bar magnets have fascinated us for centuries due to their practical applications in everyday tools and advanced technologies. In this article, we will dig deep into What a is Bar Magnet, the Properties of the Bar Magnet, the Application of Bar Magnet, and others in detail.

What is Bar Magnet?

A bar magnet is a rectangular piece typically made from iron, steel, or a ferromagnetic substance, having distinct north and south poles. Even if it's broken, each fragment will maintain its unique identity with retained poles.

Bar Magnet Diagram

The basic diagram of the Bar Magnet is added in the image below,

Poles of Bar Magnet

A bar magnet has two poles:

• North Pole
• South Pole

These poles play an important role in magnet's behavior and interactions.

Types of Bar Magnet

Various types of the bar magnets are added in the article below,

• Alnico Bar Magnet
• Neodymium Bar Magnet
• Cylindrical Bar Magnet
• Rectangular Bar Magnet

Alnico Bar Magnet

Alnico bar magnets offer excellent temperature stability, high residual induction, and relatively high energies. They have better corrosion resistance and usually do not require surface treatment. ​It has temperature stability, with a working temperature of 300-500°C, and they demagnetize at temperatures exceeding 600°C. Due to their strategic resources of cobalt and nickel, alnico magnets are relatively expensive and find applications in aerospace, military, automotive industry, and security systems.

Neodymium Bar Magnet

Neodymium bar magnets are widely used in electronics, electrical machinery, medical equipment, toys, packaging, hardware machinery, aerospace, and other fields. They are known for their exceptional magnetic strength and versatility, making them popular in various industries and scientific applications. Neodymium bar magnets come in a range of grades, offering exceptional magnetic strength and adaptability. However, they are sensitive to temperature and can be significantly affected by exposure to elevated temperatures.

Cylindrical Bar Magnet

A bar magnet of the shape of a cylinder is called a cylindrical bar magnet. It is also called Rod Magnet.

Rectangular Bar Magnet

Normal bar magnet that is in shape of a cuboid is called a Rectangular bar magnet. It has various applications and in general is called Bar mangnets.

Properties of Bar Magnet

Various properties of a Bar Magnet are,

• Directional Property: When suspended freely a Bar Magnet always comes to rest in the geographically north-south direction.
• Magnetic Induction: When a magnetic material is kept in contact with a bar magnet, it acquires magnetic properties through magnetic induction.
• Demagnetization: A bar magnet loses its magnetism when heated, beaten hard by a hammer, or kept under AC current.
• Attractive Property: The bar magnet attracts ferromagnetic materials like iron, cobalt and nickel.
• Existence as a Dipole: Bar magnet always exists as a dipole, and the existence of a monopole is not possible

Magnetic Field of a Bar Magnet

Magnetic field of a bar magnet is created by the motion of electrons in the material that forms the magnet. It's Magnetic force is strongest at the poles. The magnetic field of a bar magnet is very similar to the electric field created by an electric dipole.

The magnetic field of a Bar Magnet is shown in the image added below,

Magnetic Field Lines Around a Bar Magnet

Magentic field lines are the imaginary lines that are used to represent the strength of a magnet. These lines start from the north pole of the magnet and goes to the south pole of the agent. Properties of the magnetic field are added below,

• For a bar magnet, the magnetic field lines form closed loops, extending from the north pole to the south pole.

When two bar magnets are brought close to each other, their magnetic lines of force interact with each other and get modified to point in the direction of the resultant magnetic force (field).

Pole Strength of Bar Magnet

The pole strength of a bar magnet is the strength of a magnetic pole to attract magnetic materials towards itself. The magnetic force of a bar magnet is strongest at the poles. The pole strength is related to the magnetic moment of the magnet, and it is the product of the pole strength and the length of the magnet.

Formula of Pole Strength

Formula to find pole strength of a bar magnet is given by:

P = W/T

Where,

• P is the Strength of Magnetic Pole
• W is the Work Done in Moving Magnet around the Wire
• I is Electric Current in Wire

SI Unit of Pole Strength

• SI Unit of pole strength of a bar magnet Ampere-meter (A.m).
• Dimension of Pole strength is, [LA]

Applications of Bar Magnets

Bar magnets have various applications in different fields which are as follows:

• Picking up Small Metallic Objects: Bar magnets are used to pick up small metallic objects such as metal shavings, nails, and screws, as well as magnetic stirring rods in laboratory settings.
• Industrial purposes: Bar magnets are used for industrial applications such as collecting magnetic waste or separating magnetic objects from a large area of mixed substances. They are also used for stirring mixtures to facilitate the mobility of ferromagnetic substances in chemical experiments.
• Electronic Devices: Bar magnets find applications in electronic devices such as televisions, microphones, and mobile phones.

Uses of Bar Magnet

Various uses of the bar magntes are,

• Magnetizing Objects: Bar magnets can be used to magnetize other objects such as paperclips, by stroking the object against the bar magnet
• Compass: When freely suspended the bar magnet aligns itself to earth's magnetic field making it useful as a compass to find north and south direction.

Bar Magnet as Equivalent Solenoid

A bar magnet can be modeled as an equivalent solenoid. The magnetic moment of a bar magnet as an equivalent solenoid can be derived by calculating the axial field of a finite solenoid carrying current. The similarity between magnetic field lines of a bar magnet and solenoid is that a bar magnet can be thought of as a large number of circulating currents in analogy with a solenoid. The image of magnetic field of a Solenoid is added below,

Read more about Magnetic Field of a Solenoid.

Difference between Bar Magnet and Electromagnet

The key difference between a bar magnet and an electromagnet lies in their magnetic properties:

• Electromagnet: An electromagnet, is a temporary magnet that can produce a magnetic field in the presence of electric current. It is formed when electric current is passed through wires wound around a soft metal core. The strength of the magnetic field produced by an electromagnet can be varied by controlling the electric current that passes through the wire. However, an electromagnet loses its magnetism once the current flow is stopped, requiring a continuous power supply to maintain the magnetic field.
• Bar Magnet: A bar magnet is a permanent magnet that can create its own persistent magnetic field. It has a fixed magnetic field strength and does not require an external power source to maintain its magnetism. The magnetism in a bar magnet is caused by the alignment of electron spins within the material, resulting in a constant magnetic field.

Read More,

• Magnetic Force on a Current-Carrying Wire
• Magnetic Field Strength
• Magnetism

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Article Tags :

• School Learning
• Class 10
• School Physics
• Physics-Class-10
• PCM

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